The present invention relates to an air conditioner for vehicles and, more particularly, to an air conditioner system in which the temperature of air flowing into the evaporator of the air cooler is detected and the set temperature of the evaporator is changed to compensate for the change in the detected air temperature.
In the conventional air conditioner for vehicles, the air temperature in or around the evaporator is detected by a thermostat and the compressor is turned on and off so as to maintain the air temperature at the set level. The thermostat is usually set to operate at a temperature around 0.degree. C., in order to prevent frosting or icing of the evaporator.
In current automative air conditioners, the control of temperature of air blown into the passenger's compartment is effected by a so-called air mix type system in which the air cooled and dehumidified by the evaporator is again heated to a suitable temperature by a heater before the air is discharged into the compartment.
In such a case, once the air conditioner switch is turned on, the compressor is operated repeatedly such that the evaporator temperature is maintained around 0.degree. C. Therefore, the compressor operates frequently even in the seasons in which the demand for cooling is not so large, e.g., spring, autumn and winter. In consequence, the fuel consumption is increased and the driveability of the automobile deteriorates disadvantageously.